Telescopic sections for mobile crane jibs are known for example from DE 198 11 813 A1. In this known mobile crane jib, the locking bolts are guided in an inner telescopic section and pretensioned radially outwards by means of a spring. Thus, the locking bolt is designed on its outer end such that it can engage in a receiver provided in an outer telescopic section surrounding the inner telescopic section. Furthermore, a release device is provided which engages with the inner end of a locking bolt in order to release the locked position thereof against the spring biasing.
The actuation of the locking bolts is effected by means of a hydraulic drive. A disadvantage of this is that hydraulic lines are required which must be passed inside or outside the telescopic jib to the locking system. This involves an increased amount of space, more weight and assembly work which are in turn associated with additional costs. Furthermore, the build up of pressure within the hydraulic lines is dependent on various external influences, particularly the temperature and line length when using a telescopable oil guide. Moreover, valves are required to control such locking and these make additional laying of electric cables in the locking system necessary.